These investigations represent the continuation of our studies on the factors which may influence the differentiation and growth of the exocrine and endocrine pancreas of the rat. Development of the pancreas in vivo as well as in vitro will be quantitated by sensitive and specific morphologic techniques at both the light and ultrastructural levels and by biochemical indices of differentiation. The influence of maternal diabetes and hypersomatotrophic states will also be quantitated. Under more controlled in vitro conditions the effects of such environmental factors as nutrient composition, atmosphere and pH, as well as specific hormones and secretogogues will be quantitated. Alternative methods of culture -- watchglass and continuous flow perfusion -- will also be evaluated. By these studies we hope to gain basic information on the control of cell growth and differentiation; vital information which will be applicable not only to these specific pancreatic tissues but to tissues in general.